Various techniques have been developed for correcting geometric distortion that occurs when an image (video) projected by a projection-type projector apparatus is viewed from a user's viewpoint.
For example, a video projection apparatus capable of correcting image distortion due to the distortion of a screen itself is known. Such a video projection apparatus projects a test image from a projector onto the screen, captures the projected test image with a camera-equipped cellular phone, and performs geometric correction based on the image captured by the camera-equipped cellular phone. This allows the video projection apparatus to correct distortion(s) (geometric distortion(s)) of the video due to the distortion of the screen itself.